In his book Succeeding, John Reed wrote one of the smartest things I’ve ever read:

When you first start to study a field, it seems like you have to memorize a zillion things. You don’t. What you need is to identify the core principles – generally three to twelve of them – that govern the field. The million things you thought you had to memorize are simply various combinations of the core principles.

This extends beyond those learning a new field. I think it’s most relevant for those who consider themselves experts. The root of a lot of professional error is ignoring simple ideas that seem too basic for those with experience to pay attention to.

Having seen the investing world from several different angles, four skills stand out as governing most of outcomes.

1. The ability to distinguish “temporarily out of favor” from “wrong.”

The two strongest forces in investing are “This investment looks broken because that’s how opportunity presents itself” and “This investment looks broken because it’s actually broken.” It’s hard to tell the difference in real time. Distinguishing between the two relies on accurately calculating the odds that something will eventually come along to heal or promote the market or company that looks broken. And since those odds are always less than 100%, it can take a while to tell if you’re any good at it, because even when the odds are in your favor the outcome can go the wrong way. It’s hard to do. But worse, and more common, is forgetting that a distinction needs to be made in the first place.